JP4683916B2 - Optical isolator - Google Patents

Description

  The present invention relates to an optical isolator used in an optical communication technology for small devices and a method for manufacturing the same.

  Optical isolators are used in optical amplifiers, semiconductor laser devices, and the like. In this optical isolator, the relative angle between two polarizers is set to about 45 °, and a Faraday rotator with a Faraday rotation angle of about 45 ° is inserted between them to fix them together. It has a function of transmitting light and blocking light in the reverse direction.

  In recent years, there has been a strong demand for miniaturization, mass production, and cost reduction for this optical isolator. For example, the optical isolator disclosed in Patent Document 1 has been developed and used as a countermeasure. .

  As shown in FIG. 6, the optical isolator element 10 includes polarizers 1 and 3 and a Faraday rotator 2, and a rectangular parallelepiped magnet 4 is bonded and fixed to a single flat plate-like alignment substrate 5 with alloy solder. What has a structure is disclosed.

  Further, as shown in FIG. 7 disclosed in Patent Document 2, an optical element including polarizers 1 and 3 and a Faraday rotator 2 and a rectangular parallelepiped magnet 4 are bonded to an alignment substrate 5 having different steps by a bonding material 7. -The thing with the fixed structure is also disclosed.

The optical isolator having such a configuration can be easily mounted on a TEC (Thermoelectric Cooler), easily downsized, etc., when it is mounted in an LD (Laser Diode) module. It is considered superior.
JP-A-10-227996 JP 2001-264695 A

  However, in the structure in which the magnet and the optical element are arranged on the plane as described above, the bonding material is dropped on the alignment substrate, and the optical element and the magnet are arranged on the bonding material. When the position deviates from a desired position, the bonding material protrudes from the front surface of the alignment substrate and moves to the back surface, and cannot be detached from the jig when the bonding material is cured.

  Even if the alignment substrate has a guide structure for positioning, if the amount of dripping is large in order to place the optical element or magnet on the bonding material, the optical element or magnet may be displaced from a predetermined position on the alignment substrate. However, it protrudes from the alignment substrate, so that the joining accuracy becomes difficult and the effective opening diameter cannot be secured.

  The conventional optical isolator needs to tilt the entire optical isolator with respect to the optical axis in order to prevent the near-end reflected return light to the LD, and uses a larger space in the LD module, thereby preventing the miniaturization of the LD module. There was a problem to become.

  Further, since the LD module and the lens and the optical isolator arranged in the immediate vicinity of the LD are individually aligned and arranged, there are problems that man-hours increase and miniaturization is hindered.

  The object of the present invention has been devised in view of the above-described problems, and is an optical isolator that realizes high-precision bonding, enables downsizing and cost reduction, and eliminates problems occurring during assembly. Is to provide.

In view of the above problems, an optical isolator according to the present invention is an optical isolator in which an optical component including an optical isolator element including at least a polarizer and a Faraday rotator is bonded to an alignment substrate via a bonding material. A recess having an opening area smaller than the area of the joint surface of the optical component is formed at the center of the surface on which the optical component is mounted, and the surface tension is applied from the periphery of the joint surface of the optical component while filling the recess. The bonded optical component is bonded through the bonding material that protrudes minutely within a range that can be maintained .

As an optical isolator manufacturing method, in an optical isolator manufacturing method in which an optical component including an optical isolator element including at least a polarizer and a Faraday rotator is bonded to an alignment substrate via a bonding material, A recess having an opening area smaller than the bonding surface of the optical component is formed at the center of the surface on which the optical component is mounted, and the bonding material overflows from the surface and reaches a dripping amount that reaches the bonding surface. After the optical component is placed on the bonding material, the optical component is allowed to protrude from the periphery of the bonding surface within a range in which the surface tension can be maintained , and then the bonding material is cured so that the optical component, the alignment substrate, It is characterized by joining.

According to the configuration of the present invention will be joining the optical science component including an optical isolator element through the bonding material on the alignment substrate, the bonding material is filled into the recess opening area smaller than the area of the junction surface of the optical component because they are, the optical components are compact, when projecting a bonding material filled in the concave portion from an opening surface of the concave portion, since the optical component is moved to the center position of the recess on the alignment substrate by surface tension position Because it can prevent misalignment and can be joined without shifting the optical axis, it can be further reduced in size compared to the conventional structure, and the optical isolator element can be arranged without adjustment. An optical isolator with a high yield and a low cost can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol shall be used about the same thing as a prior art.

  1A and 1B are views for explaining the structure of an optical isolator according to the present invention. FIG. 1A is a schematic perspective view of the optical isolator according to the present invention during assembly, and FIG. 1B is a perspective view of an assembled product after bonding and fixing. .

  The optical isolator of the present invention is formed by bonding an optical component X including an optical isolator element 10 onto an alignment substrate 5 via a bonding material 7.

  The alignment substrate 5 has an optical isolator element 10 and an optical component X including the magnet 4 mounted on the substantially central portion (in the figure, the optical isolator element 10 is mounted at the center of the alignment substrate 5 and the magnets 4 are mounted at both ends thereof. Is provided with a recess 6 having an opening area smaller than the joint surface of the optical isolator element 10 and the magnet 4. Here, the bonding surface refers to the entire area of the lower surface of each optical component X.

  The bonding material 7 is dropped and filled on the recess 6 so as to overflow the opening area of the recess 6 and protrude from the opening. Further, the bonding material 7 overflowing from the recess 6 is expanded so as to have an area smaller than the bonding area of the optical isolator element 10 and the magnet 4, and the optical isolator element 10 and the magnet are placed on the bonding material 7 as will be described in detail later. Press 4 to place.

  The material of the alignment substrate 5 used in the present invention is preferably close to the thermal expansion coefficient of the Faraday rotator 2 to be described later in order to stabilize the optical characteristics of the optical isolator, such as 50Ni-Fe, SUS430, SF20T. Metals such as zirconia and ceramics such as zirconia are desirable. In the case of metal, it can be manufactured by MIM molding in addition to precision processing such as cutting and end milling.

  In order to increase the bonding force of the bonding material 7, the bonding surfaces 8 and 9 are preferably subjected to shot blasting or matte processing in addition to roughening the surface roughness for the purpose of increasing the bonding area or anchoring effect. Further, when the optical isolator element 10 and the magnet 6 are directly bonded via the bonding material 7, cracks may occur in the polarizers 1 and 3 due to a difference in thermal expansion coefficient. For this reason, it is desirable that the bonding surface 8 and the bonding surface 9 have a step structure as a structure that is not physically bonded. However, there is no limitation as long as there is a method in which both are not bonded by a jig or the like.

  The optical isolator element 10 includes polarizers 1 and 3 that absorb a polarization direction orthogonal to a transmission polarization direction, such as a type in which dielectric particles are included in a glass substrate or a dielectric laminated type, and Bi added with Tb, Gd, or Ho. It is composed of a Faraday rotator 2 made of a substitution garnet or a YIG garnet, and is rotated and aligned in advance so that the angle of the transmission polarization plane of the polarizers 1 and 3 is 45 °, and then bonded and fixed by a bonding material.

  This optical isolator element 10 is formed by cutting into a predetermined size on the bonding surface 8 in consideration of securing the light beam area of the signal light from the LD module and accommodating it in the bonding surface 8 of the alignment substrate 5. Bonded and fixed. The magnet 4 for imparting a sufficient saturation magnetic field strength to the Faraday rotator 2 is preferably an Sm—Co based or Nd—Fe—B based magnet made of a rectangular parallelepiped excellent in heat resistance of the magnetic field strength.

  Since the magnet 4 is a sintered body, there is a possibility that the powder hits the magnet surface at the time of production, and may block the optical path of the optical isolator as a foreign substance. May break. In order to prevent them, it is desirable to plate Ni or the like on the surface of the magnet.

  However, when the Faraday rotator 2 having a self-coercive force is used as the Faraday rotator 2, the magnet 4 is not necessary.

  Further, FIG. 2A is a schematic perspective view of the optical isolator of the present invention shown in FIG. 1A in which the lens 21 is disposed on the alignment substrate 5 on the incident side of the optical isolator element 10 as the optical component X. It is. The alignment substrate 5 has an opening area smaller than the joint surface of the optical isolator element 10 and the lens 21 at the center line of the joint surface 8 on which the optical component X including the optical isolator element 10 and the lens 21 is mounted, and the optical isolator element 10. A groove 20 facing both the lenses 21 is provided. Here, the bonding surface 8 refers to the entire area of the lower surface of each optical component X.

  As in the embodiment of FIG. 1, the bonding material 7 is dropped and filled on the groove 20 so as to overflow the opening area of the groove 20 and protrude from the opening. Further, the bonding material 7 overflowing from the groove 20 is expanded so as to have an area smaller than the bonding area between the optical isolator element 10 and the magnet 4, and the optical isolator element 10 and the lens 21 are disposed on the bonding material 7. FIG. 2B is a perspective view of the assembled product after adhesion and fixing.

  FIG. 3 shows a bonding state between the bonding surface 8 and the bonding material 7 of the optical isolator element 10 and the alignment substrate 5 of the present invention. The bonding material 7 is dropped onto the concave portion 6 formed in the substantially central portion of the bonding surface 8 using a dispenser. The amount of dripping is appropriately set by adjusting the viscosity of the bonding material 7, the air pressure of the dispenser, and the diameter of the needle hole of the cylinder (not shown) containing the bonding material 7, and protrudes from the opening surface of the recess 6. The recessed portion 6 can be largely filled, and the amount of dripping is smaller than the adhesion surface of the optical isolator element 10. As shown to (a), the optical isolator element 10 was arrange | positioned and contacted so that the center position of the joint surface of the optical isolator element 10 and the center position of the dripped joining material 7 might correspond. Due to the weight of the optical isolator element 10, the bonding material 7 spreads on the optical isolator element 10 to the bonding surface 8. However, due to the surface tension, the bonding material 7 protrudes slightly from the optical isolator element 10 within the range where the surface tension can be maintained as shown in FIG. Or it does not protrude from the contact surface with the optical isolator element 10 as shown in (c), and even if the optical isolator element 10 has a very small size, the concave portion 6 can be set substantially at the center.

  When the optical isolator element 10 is brought into contact with the bonding material 7, the optical isolator element 10 may be pressed, but when the pressure is too large or when the pressure is not perpendicular to the bonding surface 8, Since the bonding material 7 may protrude from the contact surface of the optical isolator element 10 and may protrude from the bonding surface 8, it is preferable to leave the bonding material 7 under its own weight without pressing. The same applies to the bonding between the magnet 4 and the bonding surface 9 of the alignment substrate 5.

  FIG. 4 shows a top view of the optical isolator of the present invention. In order to suppress return light due to near-end reflection to the semiconductor laser element, the optical isolator element 10 is inclined by 4 to 10 degrees with respect to the optical axis. The lateral width of the bonding surface 8 of the alignment substrate 5 is appropriately set so that the optical isolator element 10 does not protrude. Similarly, as shown in the optical isolator of the present invention in FIG. 5, the optical isolator element 10 is not a rectangular parallelepiped shape shown in FIG. 4, but a parallelogram shape as viewed from the top view, and the incident surface and the outgoing surface are inclined with respect to the optical axis It may be a square pole.

  The optical isolator having such a configuration is mounted on a TEC (Thermoelectric Cooler), which can easily align the transmission polarization direction when mounted in an LD (Laser Diode) module.

  Hereinafter, 100 optical isolators shown in FIG. 1 as an example of the present invention and 100 optical isolators shown in FIG. 7 as a conventional example were manufactured, and yields were compared.

  In FIG. 1, it is made of 50Ni—Fe and has a width of 3 mm (width of the joint surface 8; 1.2 mm, width of the joint surface 9; 0.9 mm) × depth of 2 mm × height of the joint surface 8 of 0.4 mm (joint). In the alignment substrate 5 having a height 9 mm of the surface 9, a recess 6 having a diameter of 0.2 mm and a countersink depth of 0.1 mm was provided at the center of each of the bonding surfaces 8 and 9. The joint surfaces 8 and 9 are processed by shot blasting to roughen the surfaces. On the other hand, the optical isolator element 10 was formed by cutting into a rectangular solid of □ 0.9 mm × thickness 0.8 mm in order to include the beam diameter of the light emitted from the semiconductor laser, which is φ0.8 mm. Before the optical isolator element 10 is cut and formed, the polarizer 1, the Faraday rotator 2, and the polarizer 3 are rotated and aligned in advance so that the angle of the transmission polarization plane of the polarizers 1 and 3 is 45 °, and then bonded. It is bonded and fixed by the material.

  The bonding material 7 was dropped onto the concave portion 6 of the bonding surface 8 by a dispenser, and the bonding material 7 was disposed thereon so as to coincide with the substantially central portion of the optical isolator element 10, and the bonding material was cured and fixed by heating. At this time, the transmission polarization plane of the polarizer 1 is installed so as to be parallel to the bonding surface 8 of the alignment substrate 5.

A rectangular parallelepiped magnet 6 (width 0.8 mm × depth 1.8 mm × height 1.2 mm) for applying a magnetic field to the Faraday rotator 2 is made of Sm—Co, and the surface thereof is plated with Ni. .

Similarly, the bonding material 7 was dropped onto the concave portion 6 of the bonding surface 9 by a dispenser, and the bonding material 7 was arranged on the concave portion 6 so as to coincide with the substantially central portion of the magnet 6, and the bonding material was cured and fixed by heating. Although a thermosetting bonding material is used this time, an ultraviolet curable bonding material or a visible curable bonding material that can ensure bonding strength may be used.

  The alignment substrate 5 of the optical isolator of the conventional example shown in FIG. The manufacturing method is the same as that of the embodiment of the present invention.

Table 1 shows a comparison between the optical isolator of the conventional example and the optical isolator of the present invention in terms of the yield of the optical isolator element protruding from the alignment substrate, the optical element crack, the bonding material protruding from the alignment substrate, and the magnet protruding from the alignment substrate. .

  In the optical isolator of this embodiment, since the optical isolator element 10 and the bonding material 7 are fixed to the central portion of the bonding surface 8 of the alignment substrate 5 depending on the dropping amount and positional relationship, the optical isolator element 10 is displaced and effective. Since there was no cracking of the optical element due to the small opening diameter and the joining with the magnet, it was improved by 13% and 18%, respectively, from the conventional example.

  Further, the dropped bonding material 6 is located at the center of the bonding surfaces 8 and 9, and the amount of adhesion is controlled, so that the bonding material does not protrude from the bonding surfaces 8 and 9 during bonding, and the optical isolator element 10 and Similarly, the magnet 6 can be controlled so as not to protrude from the alignment substrate 5.

  Thereby, compared with the conventional example, the protrusion of the bonding material 7 from the alignment substrate 5 and the protrusion of the alignment substrate 5 of the magnet 6 can be improved by 8% and 10%, respectively. Furthermore, since the bonding material dropping position becomes a mark for positioning the optical isolator element 10 and the magnet 6 in assembly, the working efficiency when mounted on the bonding surfaces 8 and 9 can be improved by 30% compared to the conventional example. At the same time, since the optical isolator element 10 can be easily positioned, the size of the optical isolator element 10 can be reduced as compared with the conventional example. From the above, it is possible to provide a low-cost optical isolator in this embodiment as compared with the conventional example because yield improvement, work efficiency improvement, and miniaturization are possible.

It is an assembly perspective view of the optical isolator of the present invention. It is an assembly perspective view of the optical isolator of the present invention. It is a junction schematic diagram of the optical isolator of the present invention. It is a top view of the optical isolator of the present invention. It is a top view of the optical isolator of the present invention. It is a perspective view of the conventional optical isolator. It is a perspective view of the conventional optical isolator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Polarizer 2 ... Faraday rotator 3 ... Polarizer 4 ... Magnet 5 ... Alignment board | substrate 6 ... Concave material 7 ... Bonding material 8 ... Bonding surface 9 with an optical isolator element ... Bonding surface 10 with a magnet ... Optical isolator element 20 ... Groove 21 ... Lens

Claims (2)

In an optical isolator in which an optical component including an optical isolator element including at least a polarizer and a Faraday rotator is bonded to an alignment substrate via a bonding material, a central portion of a surface of the alignment substrate on which the optical component is mounted is provided. A recess having a smaller opening area than the bonding surface of the optical component is formed, and the bonding material is filled in the recess and protrudes minutely within a range in which surface tension can be maintained from the periphery of the bonding surface of the optical component. An optical isolator, wherein the optical component is bonded. In an optical isolator manufacturing method in which an optical component including an optical isolator element including at least a polarizer and a Faraday rotator is bonded to an alignment substrate via a bonding material, a surface of the alignment substrate on which the optical component is mounted A concave portion having an opening area smaller than the bonding surface of the optical component is formed in the central portion, and the optical material is filled in the concave portion so that the bonding material overflows from the surface and reaches the bonding surface. Is placed on the bonding material , protruded from the periphery of the bonding surface within a range in which the surface tension can be maintained , and then the bonding material is cured to bond the optical component and the alignment substrate. Manufacturing method of optical isolator.

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